In program, we have:
var task1 = some task;
task1.start()
If mock the task result in unit test, the result is returned by mock mechanism immediately before calling the start(), and raise "Start may not be called on a task that has completed" exception.
How to address that issue and compose a valid unit test?
Paste a simplified sample code here for clarity, which produces the above exception:
namespace TestTaskStart
{
public class TestMethods : ITestMethods
{
public async Task<int> AlwaysReturnOne(int number)
{
return await Task.FromResult(1);
}
}
}
namespace TestTaskStart {
public class TestInvoker
{
private ITestMethods testMethods;
public TestInvoker(ITestMethods testMethods)
{
this.testMethods = testMethods;
}
public async Task<int> GetANumberWrapperTask(int number)
{
// just an exmple of one tasks to be called
var task = this.testMethods.AlwaysReturnOne(number);
task.Start();
Task.WaitAll(task);
return task.Result;
}
}
}
namespace TestTaskStart {
[TestClass]
public class UnitTests
{
ITestMethods numberGetter;
TestInvoker testInvoker;
[TestInitialize]
public void Setup()
{
this.numberGetter = Substitute.For<ITestMethods>();
this.testInvoker = new TestInvoker(this.numberGetter);
}
[TestMethod]
public void TestGetANumberWrapper()
{
this.MockAlwaysReturnOneResult();
var result = testInvoker.GetANumberWrapperTask(5).Result;
}
private void MockAlwaysReturnOneResult()
{
this.numberGetter.AlwaysReturnOne(Arg.Any<int>()).Returns(1);
}
}
}
